Equilibrium content of lanthanum in metal under the slag of СаО – SiO₂ – La₂O₃ – 15 % Al₂O₃ – 8 % MgO system

Thermodynamic modeling results of lanthanum equilibrium content in metal under the slag of CaO – SiO₂ – La₂О₃ – Al₂O₃ – MgO system corresponding to chemical composition of 16 points of local simplex plan are presented using the HSC 8.03 Chemistry (Outokumpu) software package in combination with the simplex planning lattice method. In the work, slag is represented by CaO – SiO₂ – La₂O₃ – – 15 % Al₂O₃ – 8 % MgO oxide system in a wide range of chemical composition for temperatures of 1550 and 1650 °C, and metal contains 0.06 % C, 0.25 % Si, 0.05 % Al (in this expression and hereinafter in mass.%). The results of mathematical modeling are shown graphically in the form of composition - equilibrium content diagrams of lanthanum. There is significant effect of slag basicity on the lanthanum equilibrium content in metal. An increase in slag basicity from 2 to 5 at temperature of 1550 °C leads to an increase in the lanthanum equilibrium content from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 5 % to 7 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %, hence the increase in slag basicity favorably affects development of lanthanum reduction. Increase in metal temperature also has positive effect on lanthanum reduction process. As temperature rises to 1650 °C, the lanthanum equilibrium content in metal increases from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 3 % to 12 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %. In diagrams of chemical composition of slag containing 56 – 61 % CaO, 12 – 14 % SiO₂ and 4 – 7 % La₂O₃ , the lanthanum content in metal at level of 7 – 12 ppm is ensured in temperature range from 1550 to 1650 °C. Therefore, there can be confirmed a decisive role of slag basicity, concentration of lanthanum oxide and temperature factor in development of lanthanum reduction from slags of the studied oxide system by aluminum dissolved in metal.

1. Smirnov L.A., Rovnushkin V.A., Oryshchenko A.S., Kalinin G.Yu., Milyuts V.G. Modification of steel and alloys with rare-earth elements. Part 1. Metallurgist. 2016, vol. 59, no. 11-12, pp. 1053–1061.

2. Gol’dshtein Ya.G., Efimova L.B. Modifitsirovanie i mikrolegirovanie chuguna i stali [Modification and Microalloying of Cast Iron and Steel]. Moscow: Metallurgiya, 1986, 271 p. (In Russ.).

3. Torkamani H., Raygan Sh., Garcia-Mateo C., Rassizadehghani J., Palizdar Y., San-Martin D. Evolution of pearlite microstructure in low-carbon cast microalloyed steel due to the addition of La and Ce. Metallurgical and Materials Transactions A. 2018, vol. 49А, no. 10, pp. 4495–4508.

4. Torkamani H., Raygan Sh., Garcia-Mateo C., Rassizadehghani J., Palizdar Y., San-Martin D. Contributions of rare earth element (La, Ce) addition to the impact toughness of low carbon cast niobium microalloyed steels. Metals and Materials Int. 2018, vol. 24, no. 4, pp. 773–788.

5. Liu C., Revilla R.I., Liu Z., Zhang D., Li X., Terryn H. Effect of inclusions modified by rare earth elements (Ce, La) on localized marine corrosion in Q460NH weathering steel. Corrosion Science. 2017, vol. 129, pp. 82–90.

6. Wang L., Lin Q., Ji J., Lan D. New study concerning development of application of rare earth metals in steels. Journal of Alloys and Compounds. 2006, vol. 408-412, pp. 384–386.

7. Wang L.-M., Lin Q., Yue L.-J., Liu L., Guo F., Wang F.-M. Study of application of rare earth elements in advanced low alloy steels. Journal of Alloys and Compounds. 2008, vol. 451, no. 1-2, pp. 534–537.

8. Liu H.-L., Liu C.-J., Jiang M.-F. Effect of rare earths on impact toughness of a low-carbon steel. Materials and Design. 2012, vol. 33, no. 1, pp. 306–312.

9. Yang Xi., Long H., Cheng G., Wu C., Wu B. Effect of refining slag containing Ce2O3 on steel cleanliness. Journal of Rare Earths. 2011, vol. 29, no. 11, pp. 1079–1083.

10. Wu C., Cheng G., Long H., Yang X. A thermodynamic model for evaluation of mass action concentrations of Ce2O3-contained slag systems based on the ion and molecule coexistence theory. High Temperature Materials and Processes. 2013, vol. 32, no. 3, pp. 207 – 214.

11. Yang J., Hao F., Li D., Zhou Y., Ren X., Yang Y., Yang Q. Effect of RE oxide on growth dynamics of primary austenite grain in hardfacing layer of medium-high carbon steel. Journal of Rare Earths. 2012, vol. 30, no. 8, pp. 814–819.

12. Gou J., Wang Y., Wang C., Chu R., Liu S. Effect of rare earth oxide nano-additives on micro-mechanical properties and erosion behavior of Fe-Cr-C-B hardfacing alloys. Journal of Alloys and Compounds. 2017, vol. 691, pp. 800–810.

13. Zhang F., Chen Y., Wang Y., Dong F., Wu M. Influence of La2O3 on crystallization behavior of free-fluoride mould flux and heat transfer of slag films. Journal of Rare Earths. 2011, vol. 29, no. 2, pp. 173–177.

14. Hao F., Liao B., Li D., Dan T., Ren X., Yang Q., Liu L. Effects of rare earth oxide on hardfacing metal microstructure of medium carbon steel and its refinement mechanism. Journal of Rare Earths. 2011, vol. 29, no. 6, pp. 609–613.

15. Wu C., Cheng G., Long H. Effect of Ce2O3 and CaO/Al2O3 on the phase, melting temperature and viscosity of CaO-Al2O3-10 mass % SiO2 based slags. High Temperature Materials and Processes. 2014, vol. 33, no. 1, pp. 77 – 84.

16. Babenko A.A., Smirnov L.A., Upolovnikova A.G., Nechvoglod O.V. Thermodynamic modeling of cerium reduction from slags of CaO-SiO2-Ce2O3-15 % Al2O3-8 % MgO system with aluminum dissolved in metal. Butlerovskie soobshcheniya. 2019, vol. 59, no. 9, pp. 140–145. (In Russ.).

17. Babenko A.A., Smirnov L.A., Upolovnikova A.G., Mikhailova L.Yu. Construction of equilibrium content diagrams of cerium in metal under the slag of CaO-SiO2-Ce2O3-15 % Al2O3-8 % MgO system. Butlerovskie soobshcheniya. 2019, vol. 60, no. 10, pp. 140–145. (In Russ.).

18. Kim V.A., Nikolai E.N., Akberdin A.A. etc. Planirovanie eksperimenta pri issledovanii fiziko-khimicheskikh svoistv metallurgicheskikh shlakov. Metodicheskoe posobie [Experimental Planning in Study of Physicochemical Properties of Metallurgical Slags. Manual]. Alma-Ata: Nauka, 1989, 116 p. (In Russ.).

19. Kim V.A., Akberdin A.A., Kulikov I.S. etc. Using the simplex lattice method in construction of composition-viscosity diagrams. Izvestiya. Ferrous Metallurgy. 1980, no. 9, pp. 167–168. (In Russ.).

20. Babenko A.A., Zhuchkov V.I., Leont’ev L.I., Upolovnikova A.G., Konyshev A.A. Equilibrium distribution of boron between metal of Fe–C–Si–Al system and boron slag. Izvestiya. Ferrous Metallurgy. 2017, vol. 60, no. 9, pp. 752–758. (In Russ.).